For instance, the Japanese Laid-Open Utility Model Publication No. HEI1-118905 of 1989 discloses a conveyer unit. According to this prior art, the main conveyer unit is equipped with a number of rollers for conveying load, a drive unit such as a motor for driving the rollers, and a transmission unit comprising a pneumatic cylinder for transmitting and cutting off drive force from the drive unit to these rollers. Operations of the drive unit and the transmission unit are respectively controlled by a controller unit internally provided for the main conveyer unit.
In order to form a conveyer line by linking a plurality of conveyer units with each other, conventionally, power-supply lines for feeding power to the drive unit and the controller unit provided for each conveyer unit, signal exchange lines linked with the controller unit to transmit and receive signals to and from adjoining conveyer units, and air-supply ducts for feeding air to the transmission unit composed of a pneumatic cylinder, are discretely secured to each conveyer unit independent of adjoining conveyer units.
Since the above prior art also discretely provides the power-supply lines, signal exchange lines, and air-supply ducts independent of adjoining conveyer units, when forming complex conveyer lines, installation work involves a great deal of labor and much working time. When changing formation of the conveyer line, the operator is obliged to change the arrangement of conveyer units, power-supply lines, signal exchange lines, and air-supply ducts in order to properly restructure the conveyer line. This also obliges the operator to change software applicable to the controller unit. Since software cannot readily be changed by the operator, the layout cannot easily be changed. In addition, as the scope of automation further expands, the number of drive units and sensors further increases to result in the increased number of signal exchange lines. In consequence, proper arrangement can hardly be achieved in the operating site, and yet, completion of restructuring work may eventually be delayed.